The description of Parasitic Skin Diseases in General is from Hogg's book called A Parasitic or Germ Theory of Disease, published in 1876.
Before I fully enter upon the question of the so-called parasitic diseases of the skin, it is necessary to observe that I am about to reproduce the results of observa- tion commenced in 1856, and extending over several years, to ascertain the nature, origin, and supposed influence exercised by certain minute vegetable organisms, which the microscope has enabled us to detect in connection with human skin affections. I may likewise add, at starting, that subsequent investigations tend to confirm the conclusion at that time come to, that fungi were not necessarily the cause, but more probably the effect, of the morbific condition. It is therefore more than ever necessary that attention should be steadily directed to the elucidation of this important question whether the parasite be capable of originating a specific disease, otherwise we may be liable to mistake the shadow for the substance. At the same time, I do not deny that the spores of a fungus may aggravate a condition of disease ; that is, when an eruptive or abraded surface offers a favourable soil for the growth of a parasite, it takes root and flourishes : this is seen to occur among plants of unhealthy growth.
It is believed that there is a tendency among plants and animals to become affected by a parasitic growth ; and this may be increased by atmospherical conditions, such as those known to favour the spread of an epidemic disease. I have observed, during the prevalence of a close, moist state of the atmosphere, that fungi abound; while in an opposite condition, fine, dry weather, or brisk, frosty weather, they quite disappear. This is not remarkable, as eggs and seeds lie dormant at such times and seasons, and many forms of vegetation, as the protococcus, grow only when the air is moist, and when dry remain perfectly quiescent. Vibrio tritici, wheat- cockle, can be kept inactive for years, and the powers of the cerebrum of birds suspended by freezing. It is not surprising, therefore, that diseases of the skin, accom- panied by a parasitic growth, are rarely met with during certain states of the atmosphere. It is noticed also that seasons bring round with them especial outbursts of disease ; and perhaps this is why we find the spores of aspergittus, penicittium, and puccinia, more widely distri- buted both in town and country towards the end of the hot weather ; about autumn time they are everywhere more abundant. Among those who have taken them at this period of the year, I may name the Rev. Lord S. Godolphin Osborne, who, during the cholera visitation of 1858, exposed prepared slips of glass over cesspools, gully-holes, &c. near the dwellings of those suffering from the disease, and caught what he named aerozoa -- minute germs and spores of fungi represented in fig. 1. I have again and again amused myself by catching these floating atoms, which may be found everywhere, and in and on every conceivable thing. Even the open mouth is an excellent trap for them: of this there is ample evidence, since on the delicate membrane lining the mouth of the sucking, crying infant, and on the diphtheritic sore throat of the adult, the Oidium albicans is often discovered. The human or animal stomach is also sometimes invaded : in a certain deranged condition, the Sarcina ventriculi, and its remarkable-looking quaternate spores, seriously interfere with the functions of digestion. The same class of vegetable organism occur in connection with skin diseases. The whole genera belong to a division of acotyledonous plants, called by botanists Thallophytes and Gellulares ; plants composed of cellular tissue only, having neither stem, leaves, nor stomata, and reproduced by spores ; in fact, the lowest forms of vegetable life, which alike, from their extreme simplicity of structure, puzzle the botanist and zoologist. The fungi mostly appear as a thallus, supported upon a fine thread, with spores or seeds on the under surface of the hymenium. By far the greater part of them live in the air, a few in water, always mysteriously making their appearance upon the surface of decaying organic matter. They are very fugacious, springing up in a night, arriving at maturity by noontide, and disappearing magically. I must briefly describe one or two of the commonest of the fungi, better known as moulds, or mildews. The simplest in form and structure is the yeast plant (see fig. 2), which, in its most perfect condition, is made up of globular vesicles, measuring, when fully grown, about the -arW^h of an inch in diameter. The older cells are filled with protoplasmic granular, nucleated matter ; the nucleus rapidly increases, and nearly fills the parent cell, which then becomes ovoid ; ultimately young cells bud out and are separated from the parent. Sometimes other and smaller cells are formed within the young one before it leaves the parent globule. This process is incessantly repeated, that is, so long as a supply of food lasts. The vesicles, it appears, derive their nourishment by a process of osmose, sucking in, as it were, certain portions of the organic fluid, and chemically decomposing it; appropriating a part of its nitrogen, and giving off carbonic acid. If, however, it is placed in any adverse condition, it becomes surrounded by a layer of co
ndensed matter, resulting from the death of the germinal material, and ultimately a trace only of life remains, which, dying, takes the form of an impalpable powder, and is driven hither and thither with every breath of air.
I am justified in saying that there appears to be a difference in the results obtained by brewer's yeast and those obtained by penicillium. I cannot, however, agree with M. Pasteur that the different fermentations, the vinous, the lactous, and the acetous, are produced by different species of fungi ; nor have I discovered that brewer's yeast belongs to another genus, although it may be a different species. The difference observed is that the brewer's yeast cell is quite circular in form, pale in colour, the cell wall is thin, and its contour not so well marked ; it is filled with a granular matter, described as nuclei, varying in number from five to ten, and as soon as the solution becomes exhausted, the cell wall is ruptured, and the granular matter escapes, when, if fermentation is not soon stopped, bacterium-like bodies, vibrios, are produced, and acetous fermentation begins. In the other kind of cell, by far the more important of the two, the cell wall is thick, and its contour well marked, the interior is filled with a highly refractive protoplasmic mass, the central nucleus is faintly seen, at times is not made out until the solution is nearly exhausted, when the cell has a tendency to become ovoid in form, and sometimes considerably elongated. The cell in its early life is precisely like the German yeast cell, and which is mysteriously developed. It is doubtless identical with the fungus found floating in the air ; and when it germinates in vinous solutions, it grows to a much larger size ; under certain conditions it bears a resemblance to the fat corpuscle, and probably has been mistaken for it. I term this the albuminoid form of cell, because the presence of albumen seems to add to the vigour of its growth. But the most remarkable fact in connection with this fungus is that it produces ten per cent, more alcohol than its congener, and does not become so readily exhausted as brewer's yeast. It is impossible for me to offer any explanation of this fact ; the spores must float about in an almost impalpable dust, and it does appear that a dry powder, equally with an extract of yeast, is all that is necessary to bring about a transformation of sugar into alcohol.
It is curious also to notice that, with the exhaustion of the glucose, levulose, or dextrose, the development of vibrios or bacterium-like bodies occurs, at the same time the lactic acid change begins, and a destructive process ensues. The cell walls appear to supply food for these low forms of organisms, which ultimately die off, and are succeeded by other generations. A large quantity of albumen seems to be produced by the contact action of these aerozoa; but if this substance is greatly in excess, the solution is more prone to a destructive ferment, especially so if cellulose be present at the same time. A remarkable instance of this has been brought to light. The Batrachospermese are algae, living in a sort of albuminous envelope, and their zoospores are aggregated in cells. On placing masses of this algae in a bottle, and adding fresh water, a spontaneous ferment is soon set up, the seed-vessels burst with the disengagement of gas; after this operation the colour of the liquid changes ; it assumes a delicate pink in direct light, which deepens to a reddish hue in condensed light ; the fluid is now dichroic, it is fluorescent, and the spectroscopic appearance is one of interest : the spectrum is a well-marked one, and may ultimately assist in determining the presence of albumen in animal and vegetable solutions. It certainly appears that the physiological action set up in fluids, having an excess of albumen present, is one which differs considerably from the chemical changes observed under other conditions.
Dr.Thudichum revived a curious experiment the immediate conversion of cane sugar into grape sugar. If we take two parts of white sugar, and rub it up in a mortar, with one part of a perfectly dry solid the so-called German yeast it is transformed, as if by magic, into a flowing liquid mass a syrup. This process of forming " invert sugar " can be watched under the microscope ; the liberation of carbonic acid gas in large bubbles is seen to go on, simultaneously with the assimilation of the dextrose, and breaking up of the crystals of sugar ; the cell increases in size, as well as in refractive power ; a remarkable state of activity appears in the minute mass, which is very interesting. German yeast is a spontaneously fermented mixture of wheaten flour, or malt and water, or honey and malt. I believe, with Dr. Thudichum, that this experiment goes a long way towards " changing our view of the action of yeast in producing fermentation." The transformation is so instantaneous, " that it partakes of the nature of those actions which in chemistry are called "contact actions.' " The amount of moisture retained in the German yeast is very nearly inappreciable ; yet it must be supposed that there is a minute quantity retained, or the change would not be so very instantaneous. Is, then, the change fermentation, as we call it brought about by simple " contact action," or is it due to organic life ?
It will be seen on reference to the figures given in any frontispiece, and as I shall presently proceed to show in an experimental and I trust a satisfactory way, that the same species of fungus frequently exhibits varieties of character, as well as form, at different stages of development and under varied influences ; so much so, that neither size nor outline affords any basis for distinction into species until it has been ascertained, from extensive comparison of forms brought from different localities in the widest area over which the species can be traced, what are the average characters of the type, and what their range of variation." Dr. Bary, and also Tulasne, established the fact of a wide-spread polymorphism among fungi. One fungus is actually known to possess six different kinds of fructification, the uredo itself exhibits four, and formerly these were described as distinct species.
Extreme simplicity of structure characterises all fungi or mildews. Their reproductive organs are somewhat more complex, but less understood; and although at first sight there is a difference in the appearances presented by their fruits, yet this is not sufficient to form a basis for classification. Both in pemcillium, (fig. 5), and aspergillus, the mycelium terminates in a club-shaped head, bearing upon it smaller filaments with bead-like bodies attached to the apex, piled one upon the other, or, more properly speaking, strung together; these small bodies are termed conidia; others again are surmounted by larger spores of a discoid shape, some filled with granular matter, and others quite empty (fig. 5a). Those of aspergillus are mostly without granular matter or nucleated bodies, and are more highly refractive. The club-shaped Puccinia is the well-known smut or rust, the very rapid growth of the spores and spawn of which appear to exert an exhaustive action over the tissues of the diseased cereal on which it feeds.
On repeating experiments made during my investigations "On the Vegetable Parasites of the Human Skin," I find little difference, either in the action or results produced in sugar solutions, between yeast fungus, favus fungus, aspergillium spores, and those spontaneously produced in the sweet-wort ; they are equally capable of converting or changing levulose and dextrose into alcohol ; the chemical change is very nearly identical in either case, and the slight differences observed depend more upon the pabulum on which the spores are fed, than upon any other circumstances. Most clearly, diversity in form depends upon food, temperature, &c. ; and whether the fungus is grown upon a sickly plant, an animal tissue, or a saccharine and albuminoid solution.
Nevertheless, it is attempted to build up a theory of diseases of the skin under a class termed Dermatophyta, as a something sui generis, and quite regardless of the fact that these lowly-organized plants are thereby invested with characteristics utterly at variance with the wellknown peculiarities of the family of fungi.
My inquiry then resolves itself into a definite one, namely : Is the diseased condition of the cutaneous surface due to the ravages of a vegetable parasite? or is the appearance of the vegetation the result of disease ? This is a question upon which I propose to enter, and undoubtedly it is one of some practical importance ; for if the disease is produced by the parasite, we have only to destroy the latter and a cure is certain to follow. If, on the other hand, the parasite only acts the part of a scavenger, the province of which is to remove materies morbi, then we must seek to rectify the condition on which the disease depends, and the parasite will be starved and disappear for lack of food. Every one knows that decaying substances are the seat of fungoid life ; that the mould that infests the stores of the thrifty housekeeper, and the fungi growing in damp and rotting wood, are illustrations of this fact. These low forms of vegetable life exist on decaying matter ; the decomposing process is their food, and becomes an organizing process in them; the force arising from the decomposition becomes and is their vital force. The life of the wood has in short been transformed into the fungus. The force has changed its form ; but it is the same force in both. The fungus could not have grown if the wood had not decayed.
It scarcely admits of a doubt that all the diseases observed of late in our vines, fruits, and growing crops, are the result of some atmospheric condition, as well as an exhaustion of the plant or seed a want of vigour arising out of loss of chemical elements in the soil and the air it breathes, which predisposes the plant to become an easy prey to " the murrain " or the fungus.* The microscopic germs of these lowly-organized vegetations are produced in millions ; invisible though they be to the unaided vision, they make their presence known only when seen in myriads upon the earth, in the air, and water. Wonderfully minute are their spores, and equally wonderful their rapidity of germination and growth. The old sawn stump of a tree, after a warm and rainy night in autumn, is found covered with large agarics on the following morning. A spotless meadow has been known to be covered within forty-eight hours with puff-balls, many of which are as large as the human head; and a snow-covered country changed in a night to a deep red colour, by the protococcus nivalis, gory-dew, or red snow of the northern regions.
It will not be denied that the universality of distribution of .the fungi is in itself a fact of considerable importance, and one pointing to the belief that they are ordained to become scavengers, ready to fasten on the disintegrating particles of organized matter destroyed by disease and undergoing the chemistry of re-construction by death. A very special purpose have these minute bodies to fulfil in the economy of nature : when any animal or vegetable body sinks below the standard necessary to maintain it in tolerable vigour, fungi x themselves upon it, and, finding a suitable soil, grow and spread out their pellucid filaments in every direction and in dense masses, and in so persistent a manner as to arrest any further act of development.
In a similar way the epidermic structures of the human body may be entirely excluded by a fungoid growth from the salutary influences exerted by air and light, and prevented from giving out, exhaling, the accumulated carbonic acid, and in this way aggravate and hasten on a destructive form of disease. Such a mode of progression in the low forms of vegetation is actually seen to occur when the vine is attacked by the oidium, a fungus described by botanists as a perfect plant, but which really is an imperfect condition of one of a more complex nature. The spores fasten themselves to the outer coat of the young grape, and, although internal development may proceed for a time, the sphacelated epidermis can no longer expand, and either bursts in growth, or further development is so entirely arrested that it withers and dies. This kind of arrest and death is known to take place when a silkworm is fed on unwholesome food, or is improperly exposed to wet or damp without sunlight ; it then falls a victim to the dreaded muscardine. Animals having the highest and most perfect organization speedily succumb to similar deteriorating influences; there is no immunity when nature's laws are infringed or disregarded.
Seeing, then, that the fungi are characterised throughout nature by feeding on effete or decayed matter ; that fungi supposed to. be peculiar to certain diseases of the skin are also found in many other diseases of the cutaneous surface ; that competent observers have not been able to find them in these peculiar diseases ; that sporules and filaments, described as the cause of one definite disease, have been found in the products of another form of disease supposed to have a peculiar and distinct parasite of its own ; and that attempts to implant these parasites in a healthy skin have almost invariably failed ; one cannot but conclude that special parasites, peculiar to and productive of special diseases, do not exist. This opinion gathers strength from the therapeutical fact that the alleged parasitical affections are rarely, if ever, cured by destroying the parasite ; while they can be cured by the due administration of appropriate alternatives and tonics, which are capable of correcting the blood dyscrasia, which, in truth, originates the disease.
Pediculosis (Lousiness)
Common Skin Diseases of Children
The Anatomical Structure of the Skin
